Glow plug igniter



Jan. 16, 1962 J. J. LAWSER GLOW PLUG IGNITER Filed Oct. 29. 1957JJLAWSER NTOR. d e. %e BY WW4 rQJ-ZM ff 2,;TT0RNEYS it conductor.

United States Patent ware I Filed Oct. 29, 1957, Ser. No. 693,059

2 Claims. (Cl. 317--98) This invention relates to a glow plug igniterand more particularlyto a glow plug igniter which is especially adaptedfor use in the combustion chambers, of gas turbine engines. i

Although not so limited, the glow plug igniter of this inventionissuitable for use in the heating means of the Elastic Fluid Power Plantdisclosedin copending application Serial Number 650,446, filed April 3,1957, in the names of Willis M. Clark, Jr., and Benjamin T. Howes, andassigned to the assignee of the present invention. Glow plugs used inthis type of power plant must ignite a mixture of fuel and air whichflows past the glow plug at quite high rates from the impetus of thecompressor turbine. This high rate of flow past, the igniter has alwaysbeen a problem as the raw mixture of fuel and air tends to cool theigniter below ignition temperatures.

Under normal starting conditions, the resistance wire of a glow plugigniter must reach very high temperatures, on the order of 1500 to 3000degrees F., for a period of ten seconds or more in order to ignite thefuel-air mixture. After combustion has, been initiated and the glow plughas been deenergized, the end of the glow plug element will be exposedto high temperatures, for example, from 1400 to 1800 degrees F., forlong periods of time while the engine is operating.

The present invention provides a glow plug igniter which is admirablysuitedfor use in a gas turbine engine working under the above operatingconditions. Briefly, the invention comprises a glow plug igniter with abody which is adapted to be affixed to the combustion chamber of a gasturbine engine. Mounted within the glow plug body is a metallic sleevewhich extends from one end of the body to a point intermediate the'endsof said body. Mounted 'Within this sleeve are two electrical conductorswhich are electrically insulated from each other and from the sleeve bymeans of a refractory insulating material. A hairpin shaped electricalresistance element is positioned within the body and'is electricallyconnected at one end to oneof said conductors, and at the other end tothe other Preferably, the body extends axially beyond the end of saidresistance element to shield said element and thereby prevent unduechilling by the raw fuel-air mixture which flows by said glow plugelement prior to ig nition thereof. The body member may also have aplurality of apertures positioned therein adjacent the end of theresistance element to provide desired turbulence of the fuel-air mixtureabo ut the electrical resistance element.

An object of the present invention is the provision of a glow plugigniter for use in the combustion chamber of a gas turbine engine.

A further object of the invention is the provision of a glow plugigniter for use in the combustion chamber of a gas turbine engine inwhich the electrical resistance element is protected against unduechilling from the flow of an unignited combustible fuel mixture pastsaid glow plug.

A further object is the provision of the glow plug igniter for use in agas turbine engine in which a structure to produce turbulence ofunignited combustible fuel mixture about the electrical resistanceelement is provided.

Still another object of the invention is the provision of a glow plugigniter for use in a gas turbine engine in which the electricalconnections are made remote from the end of the glow plug which isadapted to extend into the combustion chamber of the engine.

Other objects and attendant advantages of the present invention willbecome more apparent as the specification is considered in connectionwith the-accompanying drawings in which: p FIGURE 1 shows a perspectiveview partially in section of a preferred embodiment of the invention;and,

FIGURE 2 is an enlarged partial longitudinal sectional view of a portionof the invention shown in FIGURE 1. I Referring now to the drawings inwhich like reference numerals designate like parts throughout the viewsthereof, there is shown in FIGURES 1 and 2 a preferred embodiment of theinvention in which the numeral 10 designates the body of the glow plugigniter of the present invention. The body portion 10 may be dividedinto a hexagonal shaped portion 12, a threaded portion 13 and aportionof reduced diameter 14. -The body portion 10 has an internal bore 15positioned therein which is adapted to receive a metallic sleeve 16preferably made of a high temperature metal such as stainless steel AISIType 304 or 310, or Inconel Major which is an alloy whose majorconstituents are nickel chromium 15% and iron 8%. The sleeve can beconveniently secured to the body by hydrogen brazing. This sleeve mayextend from the end of the hexagonal body portion to a pointintermediate the ends of the body, and carries a pair of conductorsdesignated by the'numerals 17 and 18, said conductors having bent outportions 21 and 22 which facilitate the making of electrical connectionsthereto. A refractory insulating material 23, for example, magnesiumoxide, is positioned within the sleeve 16 and around the conductors 17and 18 to electrically insulate the conductors from each other. Therefractory insulating material also insulates the conductors from thesleeve 16 and the glow plug igniter body.

An electrical resistance element 24, preferably of a hairpin shape, ispositioned within the bore 15 and is electrically and mechanicallyconnected at one end to the conductor 17, and at the other end to theconductor 18 by any suitable method; for example, high temperaturebrazing or butt-welding so that the support for the resistance elementis furnished by the conductors. The resistance element is preferablymade of molybdenum disilicide which has high electrical resistivity,high oxidation resistance and high bending and tensile strengths atelevated temperatures.

The electrical conductors 17 and 18 are also preferably made ofmolybdenum disilicide so that a good mechanical and electricalconnection can be made between the'electrical conductors and theelectrical resistance element by the high temperature brazing orbutt-welding processes. Other materials may be used, however, theelectrical consion which are nearly equal so that stresses are not setup in the connection between the conductors and resistance element whenthey are heated and cooled. The conductors should preferably be made twoto three times the diameter of the heating elements so that the majorityof the heating occurs in the resistance element when electrical currentis passed through the electrical conductors and the element, and so thatrelatively large areas are available at the face of the electricalconductors to facilitate connecting the resistance element thereto.

As best shown in FIGURE 2, the end of the body portion of reduceddiameter 14 extends beyond the end of the curved portion of theelectrical resistance element 24 and a plurality of apertures 25 areprovided in the body portion 14 adjacent the curved portion of theelectrical resistance element to provide desired turbulence of thefuel-air mixture in the immediate vicinity of the electrical resistanceelement. This turbulence aids materially in the ignition of the fuel-airmixture.

The provision of the body member of the glow plug extending beyond theend of the electrical resistance element prevents the resistance elementfrom becoming unduly chilled as the unignited fuel-air mixture movespast the element. It will also be noted from an inspection of thedrawings that the electrical connections between the electricalresistance element 24 and the electrical conductors 17 and 18 is in sucha position that excessive heat from the combustion chamber will notadversely affect and weaken such connection as it is located aconsiderable distance from the end of the glow plug igniter body.

When installed for operation in a gas turbine engine, the end 21 of theelectrical conductor 17 is connected to one terminal of the electricalpower source of the engine; for example, a battery, whilethe end 22 ofthe other electrical conductor 18 is connected to the other terminal ofsaid power source through any conventional switching mechanism (notshown). The igniter may be energized at the same time that thecompressor turbine of the gas turbine engine is set into operation. Theigniter remains energized until it has accomplished its purpose ofigniting a combustible fuel-air mixture which flows in the combustionchamber of the engine past the igniter. After ignition of thiscombustible mixture, the ignitier is deenergized.

Thus, the present, invention provides a simple, rugged and reliable glowplug igniter for a combustion chamber of a gas turbine engine.

I claim as my invention:

1. In. a glow plug igniter for use in a combustion cham ber of a gasturbine engine, a body having an internal bore positioned therein, saidbody having an hexagonal portion at one end thereof, a threaded portionintermediate the ends, and a portion of reduced diameter at the endopposite said hexagonal portion, a sleeve positioned in said internalbore and extending from said hexagonal portion of said body to aposition intermediate the ends of said body, said sleeve having a pairof conductors positioned therein, and a refractory insulating materialpositioned therein to electrically insulate said conductors from saidsleeve and from each other, a hairpin shaped electrical resistanceelement positioned within said internal bore terminating short of theend of said body portion of reduced diameter, one end of said resistancewire being electrically connected to one of said conductors, the otherend of said resistance wire being electrically connected to the otherconductor, said hairpin shaped resistance element having a terminalportion positioned adjacent that end of the body which is adapted to bepositioned in combustion chamber of the gas .turbine engine, said bodybeing imperforate from, a position adjacent the electrical connectionbetween said first and said second electrical conductors and saidresistance element to a position adjacent the curved terminal portion ofsaid resistance element, said body portion of reduced diameter having aplurality of apertures positioned therein immediately adjacent thecurved terminal portion of said hairpin shaped electrical resistanceelement, each of said electrical conductors extending beyond said sleeveat the end of the hexagonal portion of said body and being bentoutwardly from said sleeve to facilitate electrical connection thereto.

2. In a glow plug igniter for use in a combustion chamber of a gasturbine engine, a body having an internal bore positioned therein, saidbody having an hexagonal portion at one end thereof, a threaded portionintermediate the ends, and a portion of reduced diameter at the endopposite said hexagonal portion, a sleeve positioned in said internalbore and extending from said hexagonal portion of said body to aposition intermediate the ends of said body, said sleeve having a pairof conductors positioned therein, and a refractory insulating materialpositioned therein to electrically insulate said conductors from saidsleeve and from each other, a hairpin shaped electrical resistanceelement positoned within said internal bore terminating short of the endof said body portion of reduced diameter, one end of said resistancewire being electrically connected to one of said conductors, the otherend of said resistance wire being electrically connected to the otherconductor, said hairpin shaped resistance element having a terminalportion positioned adjacent that end of the body which is adapted to bepositioned in the combustion chamber of the gas turbine engine, theelectrical connection between said conductors and said hairpinresistance element being positioned an. appreciable distance from theend of said body portion of reduced diameter and located within saidsleeve, said body being imperforate from a position adjacent theelectrical connection between said first and said second electricalconductors and said resistance element to a position adjacent the curvedterminal portion of said resistance element,

said body portion of reduced diameter having a plurality of aperturespositioned therein immediately adjacent the curved terminal portion ofsaid hairpin shaped electrical resistance element, each of saidelectrical conductors extending beyond said sleeve at the end of thehexagonal portion of said body and being bent outwardly from said sleeveto facilitate electrical connection thereto.

References Cited in the file of this patent UNITED STATES PATENTS1,826,788 Huber Oct. 13, 1931 1,914,284 Palmer June 13, 1933 1,956,586Palmer May 1, 1934 2,149,868 Rabezzana Mar. 7, 1939 2,239,175 Unser Apr.22, 1941 2,553,975 Little s May .22, 1951 2,582,890 Stamm Jan, 15, 19522,756,811 Little July 11, 1956 2,776,394 Cuny Ian. 1, 1957 2,795,220Atwood June 11, 1957 2,941,363 Cuny et a1. June 21, 1960 FOREIGN PATENTS1,069,881 France July 13, 1954

